Simultaneous flow visualization and Reynolds-stress measurement in a turbulent boundary layer

1986 ◽  
Vol 163 ◽  
pp. 459-478 ◽  
Author(s):  
A. M. Talmon ◽  
J. M. G. Kunen ◽  
G. Ooms
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Flow Visualization ◽  
Reynolds Stress ◽  
Stress Measurement ◽  
Three Dimensional ◽  
Time Dependent ◽  
Flow Structures ◽  
Wall Region ◽  
Measured Velocity

Flow visualization and Reynolds-stress measurement were combined in an investigation of a turbulent boundary layer in a water channel. Hydrogen bubbles were used to visualize the flow; a laser-Doppler anemometer capable of measuring two velocity components was applied to measure the instantaneous value of the Reynolds stress. Owing to the three-dimensional, time-dependent character of the flow it was rather difficult to identify flow structures from measured velocity signals, especially at larger distances from the wall. Despite this difficulty a method based on the instantaneous value of the Reynolds stress could be developed for detecting bursts in the wall region of the boundary layer. By this method the three-dimensional, time-dependent character of the flow is taken into account by attributing to the same burst ejections occurring successively with very short time intervals. This identification procedure is based on a comparison on a one-to-one basis between visualized flow structures and measured values of the Reynolds stress. The detected bursts were found to make a considerable contribution to the momentum transport in the boundary layer.

scholarly journals Comparison Between Experiment and Prediction for a Subsonic Turbulent Separated Boundary Layer

1992 ◽  
Author(s):  
D. Bohn ◽  
G. H. Dibelius ◽  
Z. Sucharski
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Turbine Blade ◽  
Turbulence Models ◽  
Suction Side ◽  
Wall Region ◽  
Test Rig ◽  
Measured Velocity ◽  
Volume Calculation ◽  
Free Stream Turbulence

Experimental and theoretical investigations were conducted for examining the effects of high free-stream turbulence at a high adverse pressure gradient and of periodically unsteady perturbations on the turbulent boundary layer development along the suction side of a turbine blade. As part of the experimental test rig the blade suction side is represented by a flat plate of 550 mm length. A pressure distribution typical for a turbine blade channel is generated by a curved wall opposite to this plate. The separated region towards the trailing end of the plate is 25 % of its total length. For simulating the unsteady effect of wakes being shed from the previous blade row, a wake generator is installed in the inlet cross section of the test rig. The turbulence level is raised by a turbulence grid just ahead of the wake generator. An LDV with high spatial resolution is used for measuring averaged and fluctuating components of the velocity and turbulence related quantities in the boundary layer. New correlations for the measured velocity profiles and other flow quantities especially for the separated near wall region are presented. Two separated turbulent boundary layers in a steady stream i.e. the forementioned and that measured by Simpson as well as an unseparated unsteady turbulent boundary layer have been theoretically examined. The solutions were obtained with a finite-difference boundary layer computer code and as well as with a fully elliptic finite-volume calculation procedure. The Cebeci-Smith algebraic, the Johnson-King nonequilibrium algebraic and two variants of the k-ε turbulence models were used in these calculations. The results of the various turbulence models for these flows are compared with the experimental data.

Interaction of coherent flow structures in adverse pressure gradient turbulent boundary layers

2019 ◽  
Vol 873 ◽  
pp. 287-321 ◽  
Author(s):  
Matthew Bross ◽  
Thomas Fuchs ◽  
Christian J. Kähler
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Pressure Gradient ◽  
Adverse Pressure Gradient ◽  
Flow Structures ◽  
Wall Region ◽  
Strong Impact ◽  
Wall Flow ◽  
Log Law ◽  
Near Wall

With the aim to characterize the near-wall flow structures and their interaction with large-scale motions in the log-law region, time-resolved planar and volumetric flow field measurements were performed in the near-wall and log-law region of an adverse pressure gradient turbulent boundary layer following a zero pressure gradient turbulent boundary layer at a friction Reynolds number $Re_{\unicode[STIX]{x1D70F}}=5000$. Due to the high spatial and temporal resolution of the measurements, it was possible to resolve and identify uniform-momentum zones in the region $z/\unicode[STIX]{x1D6FF}<0.15$ or $z^{+}<350$ and to relate them with well known coherent flow motions near the wall. The space–time results confirm that the turbulent superstructures have a strong impact even on the very near-wall flow motion and also their alternating appearance in time and intensity could be quantified over long time sequences. Using the time record of the velocity field, rare localized separation events appearing in the viscous sublayer were also analysed. By means of volumetric particle tracking velocimetry their three-dimensional topology and dynamics could be resolved. Based on the results, a conceptual model was deduced that explains their rare occurrence, topology and dynamics by means of a complex interaction process between low-momentum turbulent superstructures, near-wall low-speed streaks and tilted longitudinal and spanwise vortices located in the near-wall region.

Measured Reynolds Stress Tensors in a Three-Dimensional Turbulent Boundary Layer

AIAA Journal ◽  
1978 ◽  
Vol 16 (7) ◽  
pp. 645-646 ◽  
Author(s):  
C. I. Ezekwe ◽  
F. J. Pierce ◽  
J. E. McAllister
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Reynolds Stress ◽  
Three Dimensional ◽  
Stress Tensors

Multi-Plane Characterization of the Turbulent Boundary Layer

2018 ◽  
Author(s):  
Kadeem Dennis ◽  
Kamran Siddiqui
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Turbulent Flow ◽  
Flow Direction ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Wall Region ◽  
Turbulent Structures ◽  
Turbulent Flow Structure

The boundary layers are known for their significance in several engineering systems. In particular, the inner region of the turbulent boundary layer has been shown to play a significant role in controlling the dynamics of turbulent structures that are responsible for the transport of mass, heat and momentum. While substantial work has been done in the past to characterize the structure of turbulent flow in this region, the characterization of the three-dimensional turbulent flow structure is limited. This study reports a multi-plane particle image velocimetry (PIV) approach to investigate three-dimensional dynamics of the turbulent boundary layer in the near-wall region. Planar PIV is used to capture two-dimensional fluid velocity fields in several planes with respect to the fluid flow direction. These results are used to describe three-dimensional turbulent events given by key quantities such as mean and turbulent velocities and turbulent kinetic energy.

An experimental investigation of a three-dimensional turbulent boundary layer in an ‘S’-shaped duct

1999 ◽  
Vol 393 ◽  
pp. 175-213 ◽  
Author(s):  
J. M. BRUNS ◽  
H. H. FERNHOLZ ◽  
P. A. MONKEWITZ
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Reynolds Stress ◽  
Test Section ◽  
Three Dimensional ◽  
Hot Wire ◽  
Freestream Velocity ◽  
Wire Probe ◽  
The Mean ◽  
Near Wall

This paper describes the evolution of an incompressible turbulent boundary layer on the flat wall of an ‘S’-shaped wind tunnel test section under the influence of changing streamwise and spanwise pressure gradients. The unit Reynolds number based on the mean velocity at the entrance of the test section was fixed to 106 m−1, resulting in Reynolds numbers Reδ2, based on the streamwise momentum thickness and the local freestream velocity, between 3.9 and 11 × 103. The particular feature of the experiment is the succession of two opposite changes of core flow direction which causes a sign change of the spanwise pressure gradient accompanied by a reversal of the spanwise velocity component near the wall, i.e. by the formation of so-called cross-over velocity profiles. The aim of the study is to provide new insight into the development of the mean and fluctuating flow field in three-dimensional pressure-driven boundary layers, in particular of the turbulence structure of the near-wall and the cross-over region.Mean velocities, Reynolds stresses and all triple correlations were measured with a newly developed miniature triple-hot-wire probe and a near-wall hot-wire probe which could be rotated and traversed through the test plate. Skin friction measurements were mostly performed with a wall hot-wire probe. The data from single normal wires extend over wall distances of y+ [gsim ] 3 (in wall units), while the triple-wire probe covers the range y+ [gsim ] 30. The data show the behaviour of the mean flow angle near the wall to vary all the way to the wall. Then, to interpret the response of the turbulence to the pressure field, the relevant terms in the Reynolds stress transport equations are evaluated. Finally, an attempt is made to assess the departure of the Reynolds stress profiles from local equilibrium near the wall.

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